Combined crankshaft for multi-cylinder piston engines, especially internal combustion engines

ABSTRACT

Jointed crankshaft for multi-cylinder piston engines, especially internal combustion engines, which crankshaft is split in the area of the crankpin and joined together through a butt joint by means of electron-beam welding. The crankshaft is split perpendicularly in the plane of one or more shaft journals and is provided at the butt joints of adjacent shaft journals with annular faces facing each other and, through the formation of ventilated hollow space, are joined together. An intermediate layer which serves as an adhesion joint can be interposed between the faces of the shaft journals. The crankshaft can also be provided with a drive gear having a spigot which ensures a satisfactory joint and accurate centering of the pieces to be welded.

wltv -a-n United States Patent Piech [54] COMBINED CRANKSHAFT FORMULTI-CYLINDER PISTON ENGINES, ESPECIALLY INTERNAL COMBUSTION ENGINES[72] Inventor: Ferdinand V. Piech, Gahkopf, Germany [73] Assignee: FirmaDr. h c. f. Porsche K.G.,

Stuttgart, Germany 221 Filed: May4,1970 211 Appl. No.: 34,130

l 30 I Foreign Application Priority Data 3,537,333 11/1970 Seifertetal...74/597 [451 Dec. 5, 1972 Carstens ..74/597 Canonico et al.....2l9/l2lEB S 7] ABSTRACT Jointed crankshaft for multi-cylinder piston engines,especially internal combustion engines, which crankshaft is split in thearea of the crankpin and joined together through a butt joint by meansof electron-beam welding. The crankshaft is split perpendicularly in theplane of one or more shaft journals and is provided at the butt jointsof adjacent shaft journals with annular faces facing each other and,through the formation of ventilated hollow space, are joined together.An intermediate layer which serves as an adhesion joint can beinterposed between the faces of the shaft journals. The crankshaft canalso be provided with a drive gear having a spigot which ensures asatisfactory joint and accurate centering of the pieces to be welded.

10 Claims, 2 Drawing Figures COMBINED CRANKSHAFT FOR MULTI- CYLINDERPISTON ENGINES, ESPECIALLY INTERNAL COMBUSTION ENGINES BACKGROUND OF THEINVENTION The present invention relates to a combined Crankshaft formulti-cylinder piston engines, especially internal combustion engines,and more particularly, to a combined crankshaft which is split in thearea of the crankpin and joined together through a butt joint.

Joining of crankshaft halves are known, wherein the shaft journals arecombined through tension rods or the like. This construction has thedisadvantage, however, that considerable time and energy must beexpended in the manufacture of such crankshafts and a high degree ofaccuracy must be attained. In addition, such a joining technique alwayspresents the' danger that the tension rod will develop axial clearanceas a result of heat expansion, whereby the toothconstruction is damagedand the joint loosened. With internal combustion engines in which thedriving gear is fixed against rotation between the shaft journals, ajoining of the shaft journals and gear is relatively expensive, so thatan economical fabrication thereof is virtually impossible.

SUMMARY OF THE INVENTION It is an aim of the present invention toovercome the above-mentioned problems and disadvantages by creating anassembly of the two crankshaft halves through electron-stream or beamwelding.

It is a main object of the present invention to join individual shaftjournals by simple means in such a way that the crankshaft forms atorsionally solid and undetachable unit, whereby only the welding seamhas to be ground over after joining.

The underlying problems are solved in accordance with the presentinvention by perpendicularly splitting the crankshaft in the plane ofone or more shaft journals and providing the crankshaft at the buttjoints of adjacent shaft journals with annular faces facing each otherand, through the formation of ventilated hollow space, are joinedtogether by electronstream welding.

In an advantageous manner, the joining of the shaft journals isaccomplished through the interposition of an intermediate layer servingas the adhesion joint. Preferably, the intermediate layer is formed as afoil which is positioned in the plane of the butt joints of the shaftjournals.

The hollow space extending between the shaft journals is of specialimportance insofar as it is provided with ventilating bores extendingperpendicularly to the axis of rotation. It is also advantageous toprovide the driving gear with annular joint surfaces which protrudebeyond the width of the teeth and solidly connected with the annularfaces of the shaft journals in the case of a driving gear provided withthe crankshaft.

Advantageously, the driving gear is provided with a spigot in the areaof the bearing surfaces which extend into a reamed bore in the hollowspace of the shaft journals. It is particularly advantageous that thespigot of the driving gear is provided in the area of the bearingsurface with radially extending ventilating bores.

A still further advantage resides in that the driving gear is providedwith annular relief grooves in the area adjoining the bearing surfaces.The joining of the butting or bearing surfaces of the driving gear withthe faces of the shaft journals is advantageously accomplished by meansof an annular disk arranged in the plane of the butt joint.

The advantages of the present invention reside particularly in the factthat, through the formation of the hollow space in the shaft journals ofthe crankshaft, joining by means of electron-stream welding isfacilitated especially thereby and the tension stresses created duringwelding and the shrink forces during cooling of the material areadvantageously held to a minimum.

The intermediate layer provided in the butt joint makes possible theassurance of a perfect weld with the use of carbon-free steel, whereby afurther hardening of the weld seam is additionally avoided. By the formation of the intermediate layer as a foil, it may be made of differentthickness according to the selection of the material to be weldedtogether. Further, a simple placing onto the components to be welded isattained by means of the foil.

The ventilating bores extending into the hollow space facilitate thejoint welding with the electronstream welding method considerably, sincethe air escapes through the ventilating bores and the hollow space isheld under a vacuum. A perfect joint of the welding seam is therebyattained. v

In the case of joint welding of shaft journals with a drive gear, theelectron-beam feed to the weld area is considerably facilitated throughthe selected precaution of the welding process". Further, a portion ofthe stresses in the work piece are equalized through the bearingsurfaces provided.

By providing the driving gear with a spigot, a satisfactory joint andaccurate centering of the pieces to be welded, which is required withelectron-beam welding, is obtained at the same time. By means of theradially extending ventilation bores in the spigot, the weld seam isheld securely under vacuum from the inside of the hollow space of thecrankpin so that an optimum weld joint is attained throughout the entireweld surface. Annular relief grooves are provided in the driving gear,thereby extensively avoiding axial stresses during cool ing of the weldarea. If the driving gear is made of a material other than thecrankshaft material, the electron-stream welding is accomplishedpreferably by inserting an annular disk into the butt joint. On onehand, the annular disk serves for a metallurgically exact weld jointand, on the other hand, provides for an elastic zone to absorb possiblewelding stresses.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aims, features andadvantages of the present invention will become more apparent from thefollowing description when taken in conjunction with the accompanyingdrawing which shows, for purposes of illustration only, severalembodiments in accordance with the present invention and wherein:

FIG. 1 is a partial cross-sectional side view of the present inventionshowing the joining of shaft journals of a crankshaft for an internalcombustion engine, whereby the shaft journal joint is provided with anintermediate layer below the axis of rotation X-X; and

FIG. 2 is a partial cross-sectional side view of the present inventionshowing the joining of shaft journals for a crankshaft including adriving gear, whereby the shaft journal point is provided with anannular disk below the axis of rotation XX.

DETAILED DESCRIPTION OF THE DRAWINGS joined to each other by means ofelectron-beam welding. For this purpose, the crank portions 2, 2' areprovided with shaft journals 3, 3' which are provided with recesses 4, 4in the axis of rotation X-X of the shaft journals 3, 3, whereby faces 5,5' of the shaft journals are of annular cross-section. The faces 5, 5',through formation of a hollow space 6, face each other.

Parallel to the axis of rotation XX, the hollow space 6 is connectedthrough a vent bore 7 with the atmosphere of a weld chamber. The ventbores 7 pass through the crank webs 8, 8 of the crank portions 2, 2 andmay be closed off by means of plugs 9.

A direct welded joint of crank portions 2, 2 is illustrated in FIG. 1above the axis of rotation XX. For adhesion jointing, an intermediatelayer 13 in the form of a weld foil 14 is provided in the area of thebutt joint 10 between the annular faces 11, 11' of the shaft journals12, 12', as seen below the axis of rotation XX.

As seen above the axis of rotation XX' in FIG. 2, a driving gear 16 isinserted between the annular faces 15, with the crankshaft joining. Thedriving gear is provided with a bore 18 in the axis of rotation X'X' ofthe shaft journals 17, 17' and is also provided with a spigot 19inserted into a reamed bore 20 of the shaft journals 17, 17 and centeredtherein. The reamed bore 20 extends from the annular faces 15, 15 of theshaft journals l7, 17' to the hollow space 22 common to both crankportions 21, 21

The driving gear 16 is provided with butting surfaces 23, 23' which abutagainst the faces 15, 15 of the shaft journals 17, 17. The buttingsurfaces 23, 23 extend beyond the tooth width B of the driving gear 16.In the area of the butting surfaces 23, 23, the driving gear 16 isprovided with annular relief rings 24 arranged concentrically with theaxis of rotation X'X'."

Venting bores 25 are provided in the spigot 19 arranged perpendicularlyto the butting surfaces 23, 23. For shaft journals 26, 26' having a highcarbon content or with the driving gear 16 and shaft journals 26, 26made of different metals, it is suggested that an annular disk 27 beinserted in the plane of the butt joint 28 between adjacent surfaces15", 23/15, 23 as shown below the axis of rotation XX' in FIG. 2.

For joining the crank portions 2, 2' with each other and the crankportions 21, 21 at the driving gear 16 by means of the electron-beamwelding method, the faces 5, 5 as well as surfaces 15, 23 and 15, 23 areheld against each other under a predetermined amount of pressure in adevice which serves simultaneously as a centering means. Welding isaccomplished in a welding chamber of the electron-beam welding device(not shown) under vacuum of the magnitude of 10" mm Hg. By means of thevent bores 7, 25, the required vacuum is maintained at each position ofthe butt joint 10, 28, whereby a satisfactory weld joint is possible.The vent bores 7 are closed with plugs 9 after the welding process hasbeen completed.

Since the welding method is performed in a vacuum, the electron-beamwelding technique is very suitable for joining heat-resisting metalssuch as, for example, tungsten, niobium, molybdenum and tantalum as wellas the easily oxidizing metals such as beryllium, titanium and zircon inaddition to the vacuum-melted alloys.

If the shaft journals 12, 12', 26, 26' consist of a metal with a highcarbon content, a material is selected for the intermediate layer 13 orannular disk 27 of largely pure nickelor vanadium alloy in order toaccomplish a weld-joining. In the process of welding of the butt joints10, 28, the intermediate layer 13 or the annular disk 27 prevent themartensite formation of the shaft journals 12, 12, 26, 26 to be welded,that is, the intermediate layer 13 or the annular disk 27 respectivelyalloys the adjacent surfaces 11, 11', 15", 23 and 15", 23' for a bettercomposition during the welding process so that later cracks formedduring heat treatment'are avoided. The intermediate layer 13 and theannular disk 27 form, at the same time, an elastic zone and avoidthereby a hardness formation in the weld seam. By means of the annularrelief grooves 24 of the driving gear 16, stresses in the workingmaterial which occur during and after the welding process are largelyavoided.

While I have shown and described several embodiments in accordance withthe present invention, it is to be clearly understood that the same issusceptible of numerous changes and modifications as will be apparent toone of ordinary skill in the art and I, therefore, do not wish to belimited to the details shown and described herein but intend to coverall such changes and modifications as are encompassed by the scope ofthe present invention.

Iclaim:

1. Jointed crankshaft for multi-cylinder piston engines, especiallyinternal combustion engines, having shaft journals and a drive gearbetween the shaft journals, characterized in that the drive gear isprovided with annular butting surfaces which extend beyond the toothwidth of the drive gear and are fixedly connected with the annular facesof the shaft journals.

2. Jointed crankshaft according to claim 1, wherein the shaft journalsare provided with a hollow space having a reamed bore, and the drivegear is provided with spigot means in the area of its butting surfacesextending into the reamed bore.

3. Jointed crankshaft according to claim 2, wherein the spigot means isprovided, in the area of the butting surfaces, with radially arrangedvent bores.

4. Jointed crankshaft according to claim 1, wherein the drive gear isprovided, in the area of the adjacent butting surfaces, with annularrelief groove means.

5. Jointed crankshaft according to claim 4, wherein the shaft journalsare provided with a hollow space having a reamed bore, and the drivegear is provided with spigot means in the area of its butting surfacesextending into the reamed bore.

6. Jointed crankshaft according to claim 5, wherein the spigot means isprovided, in the area of the butting surfaces, with radially arrangedvent bores.

7. Jointed crankshaft according to claim 1, wherein annular disk meansare arranged in the plane of the butt joints for joining the buttingsurfaces of the drive gear with the faces of the shaft journals.

spigot means in the area of its butting surfaces extending into thereamed bore.

10. Jointed crankshaft according to claim 9, wherein the spigot means isprovided, in the area of the butting surfaces, with radially arrangedvent bores.

* IF i

1. Jointed crankshaft for multi-cylinder piston engines, especiallyinternal combustion engines, having shaft journals and a drive gearbetween the shaft journals, characterized in that the drive gear isprovided with annular butting surfaces which extend beyond the toothwidth of the drive gear and are fixedly connected with the annular facesof the shaft journals.
 2. Jointed crankshaft according to claim 1,wherein the shaft journals are provided with a hollow space having areamed bore, and the drive gear is provided with spigot means in thearea of its butting surfaces extending into the reamed bore.
 3. Jointedcrankshaft according to claim 2, wherein the spigot means is provided,in the area of the butting surfaces, with radially arranged vent bores.4. Jointed crankshaft according to claim 1, wherein the drive gear isprovided, in the area of the adjacent butting surfaces, with annularrelief groove means.
 5. Jointed crankshaft according to claim 4, whereinthe shaft journals are provided with a hollow space having a reamedbore, and the drive gear is provided with spigot means in the area ofits butting surfaces extending into the reamed bore.
 6. Jointedcrankshaft according to claim 5, wherein the spigot means is provided,in the area of the butting surfaces, with radially arranged vent bores.7. Jointed crankshaft according to claim 1, wherein annular disk meansare arranged in the plane of the butt joints for joining the buttingsurfaces of the drive gear with the faces of the shaft journals. 8.Jointed crankshaft according to claim 7, wherein an electron-beam weldedjoint is provided for joining together the split crankshaft.
 9. Jointedcrankshaft according to claim 8, wherein the shaft journals are providedwith a hollow space having a reamed bore, and the drive gear is providedwith spigot means in the area of its butting surfaces extending into thereamed bore.
 10. Jointed crankshaft according to claim 9, wherein thespigot means is provided, in the area of the butting surfaces, withradially arranged vent bores.